How to raise my GPA from a 2.90 to a 3.9 by senior year

I'm currently a Sophomore and have been doing poorly academically my whole life. I really want to get into Cornell College but my GPA isn't the greatest due to some personal issues in my life and not getting the help I needed. I want to become a mental health NP in a psychiatric clinic preferably in a mental hospital and it's just something that I feel the need to achieve. Any advice would be great and if it helps with giving the advice I have Autism and on the lower end of the spectrum I also do online schooling with a possibility to get into job corp soon.